Platelets

Platelets, also known as thrombocytes, are small, colorless cell fragments in our blood that form clots and stop or prevent bleeding. Platelets are produced in our bone marrow, the spongy tissue inside our bones. They are essential for hemostasis, the cessation of blood loss from a damaged vessel, and play a crucial role in the inflammation process.

Structure

Platelets are not true cells but are actually fragments of cytoplasm, which are derived from the megakaryocytes of the bone marrow, or lung tissue in mammals. They are small, irregularly shaped clear cell fragments, 2–3 µm in diameter, which do not have a cell nucleus. They have a life span of about 7–10 days.

Function

The primary function of platelets is to contribute to hemostasis: the process of stopping bleeding at the site of interrupted endothelium. They gather at the site and unless the interruption is physically too large, they plug the hole. First, platelets attach to substances outside the interrupted endothelium: adhesion. Second, they change shape, turn on receptors and secrete chemical messengers: activation. Third, they connect to each other through receptor bridges: aggregation.

Clinical significance

Abnormal platelet function can lead to an increased risk of bleeding or clotting. There are numerous conditions that can lead to either a decrease in platelet count or function. These include various types of hemophilia, thrombocytopenia, and thrombocythemia. In addition, certain medications can impact platelet function, such as aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs).

See also

• Blood clot
• Coagulation
• Hemostasis
• Thrombosis

References

Platelets Resources
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